A week ago, the clocks went back and while many people celebrated with a well-earned extra hour in bed, for others 60 minutes wasn’t nearly enough.

For the 7pc who suffer from seasonal affective disorder (SAD), it marks the start of what can be a long, dark period of low mood.

“As soon as you see the signs in the shop for ‘back to school’ supplies, you get this sort of dread in your stomach,” says Brian O’Connor, a company manager in his mid-40s.

“And once the hour went back, you could have invited me to the Playboy Mansion and I would have preferred to stay in and roll up socks instead.”

The Mayo Clinic describes SAD as a type of depression related to the seasons of the year, and most often beginning in late autumn and the start of winter. Sufferers experience a range of debilitating symptoms.

They may have low energy, sleep more frequently, suffer from low self-esteem and put on weight, but usually, they can manage relationships, keep going to work and maintain contact with the world around them.

“What happens is that you are not engaging with the world around you in the same way. You don’t want to answer the phone – you are cutting short calls, and ideas that may have flowed freely during summer months don’t come at all. It’s like you are reverting to being a caveman.

“You just want to go home, light a fire and hibernate, stocking up on carbs and sugar like a squirrel does nuts,” says Brian.

The good news for people with SAD is contained within the name. It is seasonal. They know that their mood will lift with the Spring lamb. “That’s also the bad news,” says Martin Rogan, the CEO of Mental Health Ireland, “because they know they have to deal with it in another year, so they look into the changing of the seasons with a sense of dread.”

“At its worst, it feels like being dead inside for three months or so,” says Liza Cox, a 29-year-old theatre maker whose move to Barcelona was partially inspired by her battle with the condition. “Then when spring rolls around, I have a feeling of coming back to life, or waking out of a dream.”

A doctor first suggested that Liza might have SAD when she was a child.

“When I was four or five years old, my mother was worried that I might have glandular fever – I was generally a very high-energy kid and one winter, when I’d just started school, I was so tired and floppy, not able to get out of bed in the morning, that she took me to get blood tests done. The tests came back fine and the doctor told her that, in his opinion, it was SAD.”

It’s something she wishes there was more dialogue around. “I’ve had friends who, without knowing my experience, have scoffed at it and called it ‘the most middle-class makey-uppy affliction’.

“It’s hard enough dealing with my own frustration with it, but trying to explain it to someone who’s not prepared to accept it makes it difficult.”

When in drama school, Liza tried to tell her movement teacher about her condition. “He was really dismissive and treated it as if it was just me not wanting to work, which was so far from the case. It has made me very wary of bringing it up with anyone in any kind of professional capacity.”

At 19, she moved to Paris and experienced a very dark winter. “I was living alone and I was exhausted and crying from pure tiredness. My parents bought me a SAD lamp for Christmas, and I think it was when I started using it and seeing the improvement it made that I realised this was something more than just in my head – there was a physical basis for this.”

Light therapy is the most well known way to combat SAD. By using light boxes specifically designed to emit a fluorescent light, it helps decrease the duration of melatonin secretion, a hormone which controls our sleep cycles and which is often secreted at the wrong time of day in people suffering from SAD.

It is also believed to boost brain neurotransmitters such as serotonin, dopamine and norepinephrine, which regulate anxiety, happiness and mood.

Brian set up Brighterday.ie, a company that imports Finish SAD lamps, in 2007, three months after he, himself, was diagnosed. “The most popular lamp is the Rondo lamp, a small round lamp you place at arms’ length and that you can flick on for 40 minutes in the morning while you are reading or working or watching TV. You don’t have to stare directly into it.”

For people who don’t have that time, he recommends the Mesa mega lamp, which will provide you with enough light in a 20-minute blast to trick your mind into thinking its bright and summery, knocking you out of hibernation mode.

“When I am using the SAD lamp, I try to use it for at least half an hour a day, in the morning preferably,” says Liza. “I’ll put it on when I’m writing or doing yoga. I really do find it helps a lot – there’s a kind of foggy feeling in the brain attached to SAD fatigue and it’s really great for clearing that. I find I have a lot more energy when I’m using it consistently.”

It’s not known for definite what causes SAD. You can be genetically predisposed to it, there may be underlying psychological reasons, or it may be a biological response to our ever-changing world.

“For humans, our natural habitat is outdoors,” says Rogan. “In winter months, our natural tendency is to slow down, to engage in a quasi-hibernation. But we live in an artificial environment and are forced to stay active. The quality of light changes, we become more reliant on artificial light, which is difficult for our bodies to handle as it’s nowhere near as strong, it’s a different temperature range and a different colour to natural light.”

While SAD lamps are effective, he recommends spending time outdoors early in the day instead, as it is much brighter than artificial light. “It will regulate melatonin and improve your sleep. While there, do some exercise, preferably aerobic – like running, skipping, cycling. It doesn’t have to be strenuous, just be outdoors for 20 minutes to half an hour.

“It can be really restorative, as it releases endorphins which increases your sense of well-being, while also increasing your metabolism, which improves energy levels.

“And put a little extra time into planning the months where you know you’re going to be down. It’s always good to have something to look forward to – one thing a week that will lift your spirits. It gives you structure and keeps you looking forward instead of backwards.”

Most importantly, according to Rogan, don’t self-diagnose. “If you have the symptoms of SAD, go to the doctor to make sure it’s not anaemia or low thyroid levels, cause if it persists, if your sleep pattern is badly impaired, if your interests or appetite begins to fade, you can become depressed as opposed to SAD.”

For Caroline Lenehan, a 33-year-old teacher, it felt like her body was trying to shut down each October. After being diagnosed with SAD by her GP, she was offered anti-depressants but instead followed the advice of a friend who had been down the road before her, investing in a light therapy box and doing bursts of exercise.

“But the best advice she gave me was ‘don’t run away from it. Yes, you’re tired, accept you have to rest and don’t be afraid to say it to people.”